SEALING OF A TURBINE RING MADE OF A CERAMIC MATRIX COMPOSITE

Abstract

Assembly in a turbine comprising: —at least one turbine ring made of a ceramic composite having a silicon carbide SiC matrix and fibers, the ring comprising a plurality of sectors (10) arranged circumferentially end to end, each of the ring sectors (10) comprises at least one circumferential edge (26, 28) provided with at least one slot (30a, 30b, 30c) opening circumferentially, —at least one sealing member being inserted for a first part into one of the slots (30a, 30b, 30c) of an edge of a first ring sector and for a second part into one of the slots (30a, 30b, 30c) of an edge of a second ring sector, circumferentially adjacent to the first ring sector, the assembly being characterized in that the sealing member is made of a ceramic matrix composite.

Claims

1. An assembly in a turbine comprising: at least one turbine ring made of ceramic material composite with a matrix and silicon carbide SiC fibres, the turbine ring including a plurality of ring sectors, arranged circumferentially end-to-end, each of the ring sectors comprises comprising at least one circumferential edge provided with at least one slot opening out circumferentially, at least one sealing member comprising a first portion inserted into one of said slots of an edge of a first ring sector and a second portion inserted into one of said slots of an edge of a second ring sector, circumferentially adjacent to the first ring sector, the assembly being characterised in that the sealing member is made of composite material with an oxide ceramic matrix.

2. The assembly according to claim 1, wherein the composite material of the sealing member comprises alumina fibres and an alumino-silicate matrix.

3. The assembly according to claim 1, wherein said sealing member has a thickness less than 1 mm thick.

4. The assembly according to claim 1, wherein the sealing member is a sealing member with a substantially planar shape.

5. The assembly according to claim 1, wherein the ring externally surrounds an annular row of moving vanes and is carried by an outer casing.

6. The assembly according to claim 1, wherein it comprises an annular row of stator vanes including inner and outer annular platforms, at least one amongst the inner and outer annular platforms being formed by said ring.

7. A sealing member intended to be arranged between two circumferential edges of two adjacent turbine ring sectors, said sealing member being characterised in that it is made of a ceramic matrix composite material.

8. The sealing member according to claim 7, wherein the two adjacent turbine ring sectors comprise a ceramic material composite with a matrix and silicon carbide SiC fibres, a plurality of ring sectors arranged circumferentially end-to-end to form a turbine ring, the two circumferential edges of the two adjacent turbine ring sectors comprising at least one slot opening out circumferentially, a first portion of the at least one sealing member inserted into one of said slots of an edge of a first ring sector and a second portion inserted into one of said slots of an edge of a second ring sector, circumferentially adjacent to the first ring sector.

9. The sealing member according to claim 8, wherein the turbine ring externally surrounds an annular row of moving vanes and is carried by an outer casing.

10. The sealing member according to claim 7, the ceramic matrix composite material of the sealing member comprising alumina fibres and an alumino-silicate matrix.

11. The sealing member according to claim 7, wherein said sealing member has a thickness less than 1 mm thick.

12. The sealing member according to claim 7, wherein the sealing member is a sealing member with a substantially planar shape.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0024] FIG. 1 is a perspective view of a turbine ring.

[0025] FIG. 2 is a perspective view of a turbine distributor.

[0026] FIG. 3 is a perspective view of a sealing member according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0027] Conventionally in a turbomachine, a moving wheel of the turbine is externally surrounded by a support ring made of an abradable material. The ring is fastened to an outer casing and is formed by a plurality of sectors arranged circumferentially end-to-end.

[0028] FIG. 1 illustrates such a ring sector 10 of a turbomachine turbine, the ring being made of CMC with a matrix and fibres of silicon carbide SiC. This ring sector 10 comprises an annular wall portion 12, herein cylindrical, including a radially outer face 14 from which extend, radially outwards, an upstream AM first radial annular wall 16 and a downstream AV second annular wall radial 18. The upstream first radial annular wall 16 and the downstream second radial annular wall 18 are provided with orifices 20 intended for fastening the ring sector 10 to the outer casing of the turbine by bolting. The ring sector 10 carries on a radially inner face 22 of the cylindrical annular wall portion 12, an abradable material layer 24 intended to cooperate with the radially outer ends of the vanes of the bladed movable wheel.

[0029] Each ring sector 10 has two circumferentially opposite edges 26, 28, facing a circumferential edge of an adjacent ring sector. Each circumferential edge 26, 28 of a ring sector 10 has at least one slot, where appropriate three slots 30a, 30b, 30c opening out circumferentially in the direction of an adjacent ring sector, and facing a slot of said adjacent ring sector.

[0030] In a particular embodiment, each circumferential edge 26, 28 comprises a first longitudinal slot 30a extending parallel to an axis X of rotation of the turbomachine.

[0031] The circumferential end 26, 28 also comprises second and third obliquely inclined slots 30b, 30c, extending according to a longitudinal component X and a radial component Z. The second and third slots 30b, 30c open out radially inwards in the first longitudinal groove 30a, and extend radially outwards at least partly across the thickness of the upstream 16 and downstream 18 radial annular walls. The second slot 30b and the third slot 30c depart from each other radially outwards. Thus, the second slot 30b extends towards an upstream edge 32, and the third slot 30c towards a downstream edge 34, of the ring sector 10.

[0032] These first, second and third slots 30a, 30b, 30c are intended to receive a sealing member 60 which, in the embodiment represented in FIG. 3, has a substantially planar shape. This sealing member may be described as a tab. Thus, these sealing tabs are inserted into the slots 30a, 30b, 30c at the circumferential ends 26, 28 of the ring sectors. The sealing tabs are partly inserted into the slots 30a, 30b, 30c of a circumferential end 26, 28 of a ring sector 10 and partly into the slots of the circumferential end of an adjacent ring sector. These sealing tabs allow guaranteeing sealing between two adjacent ring sectors 10.

[0033] FIG. 2 illustrates an example of a turbine distributor 36 sector. Conventionally, a distributor comprises an annular row of substantially radial vanes 38 connected at their radially inner ends by an inner annular platform or inner ring 40 and at their radially outer ends by an outer annular platform or outer ring 42. The distributor comprises several sectors 36 assembled circumferentially to each other, each sector 36 comprising several vanes 38 and an inner ring sector 40 or inner platform sector and an outer ring sector 42 or outer platform sector.

[0034] In a manner similar to what has been described with reference to FIG. 1, each inner 40 and outer 42 ring sector comprises two circumferential edges 52, 53, 54, 55 each including at least one slot 56, 58, two of which are not visible, into which sealing means such as tabs 60 are fitted. These tabs 60 are inserted partly into the slots 56, 57, 58, 59 of a circumferential end of an inner 40 or outer 42 annular platform sector and partly into the slots 56, 58 of the circumferential end of an inner 40 or outer 42 annular platform sector respectively. These also guarantee sealing between two sectors. Each of the inner 40 and outer 42 annular platform sectors forming a ring.

[0035] As indicated before, the sealing tabs are commonly made of a metallic material, more particularly a nickel- or cobalt-based alloy which, at high temperature, reacts with the CMC material of the ring sector 10, 40, 42. As indicated before, the use of tabs made of a metallic material poses difficulties in terms of silicide formation and oxidation.

[0036] According to the present document, it is suggested to make the tabs 60 in CMC and, more particularly, with a matrix and oxide fibres. Typically, the fibre is made of alumina and the matrix is made of alumino-silicate. The tab 60 has two circumferential edges 60a, 60b able to be inserted into said slots 30a, 30b, 30c, 56, 58.

[0037] Said tab 60 has a thickness of less than 1 mm thick and has a substantially planar shape. Indeed, because of the properties of oxide CMC, it is possible to make the tabs in the form of plates a few tenths of a mm thick. The total thickness thus being small, this makes sealing of the two ring sectors all the more easier. In turn, planarity also allows limiting air leaks.